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Rust eventually attacks any unprotected metal surface, and sanding it off is the usual precursor to painting or otherwise guarding the metal from a recurrence. The roughness of the paper you should use -- specified by its grit -- depends on the metal and how you want it to look when you're done.

Sandpaper Types

Silicon carbide -- usually known as wet/dry -- sandpaper has a tougher abrasive than garnet or aluminum oxide paper and is the best for rust removal. It's available in grits from 80 to 1,000, but for rust removal, you'll seldom need a grit finer than 320. One of the advantages of wet/dry paper is that it won't deteriorate when the surface is wet, as rusty surfaces often are.

Finer Grits Don't Scratch

The coarser the grit you use, the faster it removes rust, but the deeper the scratches it leaves. Eighty- to 100-grit is appropriate for removing rust from pipes and industrial machinery, but you shouldn't use paper coarser than 150-grit for metal furniture or fixtures that you plan to repaint. If you're preparing a car or metal appliance for painting, the lowest limit for sandpaper grit should be 220.

About the Author

Chris Deziel has a bachelor's degree in physics and a master's degree in humanities. Besides having an abiding interest in popular science, Deziel has been active in the building and home design trades since 1975. As a landscape builder, he helped establish two gardening companies.